Summary of Significant Accounting Policies - Summary of Revenue Disaggregated by Type (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation Of Revenue [Line Items]
Revenues	$ 171,208	$ 130,123	$ 103,622	$ 110,192	$ 104,056	$ 91,549	$ 86,191	$ 101,863	$ 515,145	$ 383,659	$ 235,034
Natural Gas Sales [Member]
Disaggregation Of Revenue [Line Items]
Revenues									274,239	241,379	134,618
NGL Sales [Member]
Disaggregation Of Revenue [Line Items]
Revenues									86,152	64,109	38,204
Oil Sales [Member]
Disaggregation Of Revenue [Line Items]
Revenues									138,202	74,690	50,193
Brokered Natural Gas and Marketing Revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenues									$ 16,552	$ 3,481	$ 12,019